The term medial orbital sulcus refers to a superficial feature identified by dissection on the ventral surface of the frontal lobe. In the human it constitutes the medial leg of the H-shaped orbital sulci. There it separates the medial orbital gyrus from the posterior orbital gyrus caudal to the transverse orbital sulcus and from the anterior orbital gyrus or lateral orbital gyrus rostral to that sulcus ( Mai-1997 ). In the macaque it separates the medial orbital gyrus from the lateral orbital gyrus ( Martin-2000 ). Equivalent structures are not found in the smooth cerebral cortex of the rat or mouse ( NeuroNames ).